Adjustable stiffness catheter

ABSTRACT

Medical devices such as catheters can include structure or provision that permit a physician or other health care professional to adjust the stiffness of at least a portion of the medical device. In some instances, the medical device may be adjusted prior to inserting the medical device into a patient. In some cases, the medical device may be adjusted while in use within the patient.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/218,857 filed Sep. 2, 2005, now U.S. Pat. No. 7,998,132.

TECHNICAL FIELD

The invention relates generally to medical devices such as catheters andrelates more particularly to catheters that include structure orprovision providing adjustable stiffness.

BACKGROUND

Medical devices such as catheters may be subject to a number of oftenconflicting performance requirements such as flexibility and strength.In some instances, improved flexibility may come at the expense ofreduced strength. Increased strength may come at the expense of reducedflexibility. Because each patient is unique, there may be a uniquebalance of performance parameters such as flexibility and strengthoptimal for a particular patient.

While it would certainly be possible to construct a large number ofcatheters, to accommodate any feasible set of desired performanceparameters, this would likely be cost-prohibitive. Moreover, in someinstances, a physician may determine in the middle of a procedure that aparticular balance of stiffness versus flexibility may be necessary.Therefore, a need remains for medical devices such as catheters that maybe adjusted, particularly in situ, with respect to their stiffness.

SUMMARY

The invention pertains generally to medical devices such as cathetersthat include structure or provision that permit a physician or otherhealth care professional to adjust the stiffness of at least a portionof the medical device. In some instances, the medical device may beadjusted prior to inserting the medical device into a patient. In somecases, the medical device may be adjusted while in use within thepatient.

Accordingly, an example embodiment of the invention can be found in anadjustable catheter that includes an elongate polymeric shaft extendingfrom a proximal region of the catheter to a distal region of thecatheter and a first spiral-cut hypotube that is disposed within theelongate polymeric shaft.

Another example embodiment of the invention can be found in anadjustable catheter having an elongate polymeric shaft defining a lumenthat extends from a proximal region of the catheter to a distal regionof the catheter. A first inflatable tube that extends from the proximalregion to the distal region and that is arranged at least substantiallyparallel with a longitudinal axis of the catheter is disposed within thelumen. Inflating the first inflatable tube causes the elongate polymericshaft to increase in stiffness.

Another example embodiment of the invention can be found in anadjustable catheter that includes an inner polymeric liner, an outerpolymeric liner, and a swellable layer disposed between the innerpolymeric liner and the outer polymeric liner. Adding an appropriatefluid to the swellable layer increases the stiffness of the adjustablecatheter.

Another example embodiment of the invention can be found in anadjustable catheter having an elongate polymeric shaft that extends froma proximal region to a distal region of the catheter. Astiffness-enhancing sheath that is more stiff than the elongatepolymeric shaft is slidably disposed over the elongate polymeric shaft.

Another example embodiment of the invention can be found in anadjustable catheter that includes an elongate polymeric shaft thatextends from a proximal region of the catheter to a distal region of thecatheter and that includes a wall. A number of elongate apertures aredisposed within the wall such that they extend longitudinally within theelongate polymeric shaft. Each of a number of stiffness-enhancingfilaments are slidably disposed in each of the number of elongateapertures.

Another example embodiment of the invention can be found in anadjustable catheter having an inner polymeric layer that includes one ormore electrically actuated stiffness enhancers. An outer polymeric layeris disposed over the inner polymeric layer.

Another example embodiment of the invention can be found in anadjustable catheter that includes an elongate polymeric shaft having astiffness. The stiffness of the elongate polymeric shaft can be changedby applying a current to the elongate polymeric shaft.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The Figures, Detailed Description and Examples which followmore particularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE FIGURES

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a side elevation view of a catheter in accordance with anembodiment of the invention;

FIG. 2 is a diagrammatic longitudinal cross-section of a portion of acatheter in accordance with an embodiment of the invention;

FIG. 3 is a diagrammatic longitudinal cross-section of a portion of thecatheter of FIG. 2;

FIG. 4 is a diagrammatic cross-section of a catheter in a relaxedconfiguration, in accordance with an embodiment of the invention;

FIG. 5 is a view of the catheter of FIG. 4;

FIG. 6 is another view of the catheter of FIG. 4;

FIG. 7 is a side elevation view of a catheter in a deflatedconfiguration, in accordance with an embodiment of the invention;

FIG. 8 is a side elevation view of the catheter of FIG. 7 in an inflatedconfiguration, in accordance with an embodiment of the invention;

FIG. 9 is a side elevation view of a catheter in accordance with anembodiment of the invention;

FIG. 10 is a side elevation view of a catheter in accordance with anembodiment of the invention;

FIG. 11 is a side elevation view of a catheter in accordance with anembodiment of the invention;

FIG. 12 is a side elevation view of a catheter in accordance with anembodiment of the invention;

FIG. 13 is a diagrammatic longitudinal cross-section of a catheter inaccordance with an embodiment of the invention;

FIG. 14 is a view of the catheter of FIG. 13;

FIG. 15 is a side elevation view of a catheter in accordance with anembodiment of the invention;

FIG. 16 is a side elevation view of a catheter in accordance with anembodiment of the invention;

FIG. 17 is a side elevation view of a catheter in accordance with anembodiment of the invention;

FIG. 18 is a perspective view of a catheter in accordance with anembodiment of the invention;

FIG. 19 is a diagrammatic longitudinal cross-section of a catheter in arelaxed configuration, in accordance with an embodiment of theinvention; and

FIG. 20 is a view of the catheter of FIG. 19 in an actuatedconfiguration, in accordance with an embodiment of the invention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about”, whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

The following description should be read with reference to the drawingswherein like reference numerals indicate like elements throughout theseveral views. The drawings, which are not necessarily to scale, depictillustrative embodiments of the claimed invention.

FIG. 1 is a plan view of a catheter 10 in accordance with an embodimentof the present invention. The catheter 10 can be any of a variety ofdifferent catheters. In some embodiments, the catheter 10 can be anintravascular catheter. Examples of intravascular catheters includeballoon catheters, atherectomy catheters, drug delivery catheters, stentdelivery catheters, diagnostic catheters and guide catheters. Theintravascular catheter 10 can be sized in accordance with its intendeduse. The catheter 10 can have a length that is in the range of about 100to 150 centimeters and can have any useful diameter. As illustrated,FIG. 1 portrays a guide catheter, but the invention is not limited tosuch. Except as described herein, the intravascular catheter 10 can bemanufactured using conventional techniques.

In the illustrated embodiment, the intravascular catheter 10 includes anelongate shaft 12 that has a proximal region 14 defining a proximal end16 and a distal region 18 defining a distal end 20. A hub and strainrelief assembly 22 can be connected to the proximal end 16 of theelongate shaft 12. The hub and strain relief assembly 22 can be ofconventional design and can be attached using conventional techniques.It is also recognized that alternative hub designs can be incorporatedinto embodiments of the present invention.

The elongate shaft 12 can include one or more shaft segments havingvarying degrees of flexibility. For example, the elongate shaft mayinclude a relatively stiff proximal portion, a relatively flexibledistal portion and an intermediate position disposed between theproximal and distal portions having a flexibility that is intermediateto both.

In some cases, the elongate shaft 12 may be formed of a single polymericlayer. In some instances, the elongate shaft 12 may include an innerliner such as an inner lubricious layer and an outer layer. In somecases, the elongate shaft 12 may include a reinforcing braid layerdisposed between the inner and outer layers. The elongate shaft 12 isconsidered herein as generically representing a catheter to whichvarious elements can be added to provide the catheter 10 with adjustablestiffness.

If the elongate shaft 12 includes an inner liner, the inner liner caninclude or be formed from a coating of a material having a suitably lowcoefficient of friction. Examples of suitable materials includeperfluoro polymers such as polytetrafluoroethylene (PTFE), better knownas TEFLON®, high density polyethylene (HDPE), polyarylene oxides,polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics,algins, saccharides, caprolactones, and the like, and mixtures andcombinations thereof.

The elongate shaft 12 can include, as an outer layer or layers, anysuitable polymer that will provide the desired strength, flexibility orother desired characteristics. Polymers with low durometer or hardnesscan provide increased flexibility, while polymers with high durometer orhardness can provide increased stiffness. In some embodiments, thepolymer material used is a thermoplastic polymer material. Some examplesof suitable materials include polyurethane, elastomeric polyamides,block polyamide/ethers (such as PEBAX®), silicones, and co-polymers, Theouter polymer layer can be a single polymer, multiple longitudinalsections or layers, or a blend of polymers. By employing carefulselection of materials and processing techniques, thermoplastic, solventsoluble, and thermosetting variants of these materials can be employedto achieve the desired results. In some instances, a thermoplasticpolymer such as a co-polyester thermoplastic elastomer, for example,available commercially under the ARNITEL® name, can be used.

FIG. 2 illustrates an assembly 24 that includes a hypotube 26 disposedwithin a polymeric layer 28. Merely for illustrative purposes, thepolymeric layer 28 is seen in phantom as a single layer. In some cases,the polymeric layer 28 may represent two or more polymer layers. Anysuitable polymers may be employed. It is contemplated that the assembly24 could also include one or more polymeric layers, such a lubriciouslayer, within the hypotube 26.

The hypotube 26 can be cut for flexibility purposes. In some instances,such as that illustrated, the hypotube 26 can be a spiral-cut hypotubehaving spirally-aligned cuts or kerfs 30 separating adjacent bridgeportions 32. The bridge portions 32 permit the hypotube 26 to retain acertain level of strength while the kerfs 30 lend flexibility. Thehypotube 26 can be formed of any suitable polymeric or metallicmaterial. In some instances, the hypotube 26 can be formed of stainlesssteel that has been laser cut.

Each of the kerfs 30 can be seen to have a particular width. FIG. 2 canbe assumed as showing the hypotube 26 in a relaxed configuration, i.e.no external forces are being applied to the hypotube 26. The relativedimensions of the kerfs 30 and the bridge portions 32 will provide thehypotube 26, and hence, the assembly 24, with a given balance offlexibility versus strength.

In FIG. 3, the assembly 24 has been stiffened by reducing the relativesize of each of the kerfs 34 while each of the bridge portions 32 remainunchanged. This can be accomplished by, for example, applying acompressive force to the hypotube 26, as shown by arrow 36.Alternatively, this can also be accomplished by rotating the hypotube26, as shown by arrow 38. While not expressly illustrated, it should berecognized that applying either a compressive or rotational force to thehypotube 26 may change the diameter of the hypotube 26.

In some instances, as seen for example in FIGS. 4-6, a catheter mayinclude two or more coaxially aligned hypotubes. FIG. 4 is adiagrammatic cross-section of an assembly 40, showing an inner hypotube42, an outer hypotube 44 and a polymeric layer 46. The polymeric layer46 can be formed of any suitable polymer. While not expresslyillustrated as such, the inner hypotube 42 and the outer hypotube 44 mayboth be spirally-cut. The inner hypotube 42 and the outer hypotube 44can each be formed of any suitable polymeric or metallic material. Insome instances, the inner hypotube 42 and the outer hypotube 44 can eachbe formed of stainless steel that has been laser cut.

An annular gap 48 can be seen between the inner hypotube 42 and theouter hypotube 44. It should be noted that FIG. 4 is not to scale;rather, certain elements have been exaggerated for clarity. The innerhypotube 42 can be considered as having an outer diameter that issomewhat less than an inner diameter of the outer hypotube 44. The innerhypotube 42, along with any desired inner layer or layers (notillustrated), forms a lumen 50 suitable for any desired or necessarymedical treatment.

It will be recognized that the annular gap 48 will permit at least somerelative movement between the inner hypotube 42 and the outer hypotube44 before interference between the two will decrease flexibility of theassembly 40. FIG. 4 can be considered as illustrating a relaxedconfiguration, i.e. no external forces are being applied to any portionsof the assembly 40.

In FIG. 5, however, the inner hypotube 42 has expanded relative to theouter hypotube 44 such that the annular gap 48 (seen in FIG. 4) has atleast substantially disappeared. This can be accomplished, for example,by rotating the inner hypotube 42 to expand the diameter of the innerhypotube 42. In some instances, the inner hypotube 42 may extendproximally to the proximal region 14 (see FIG. 1), or may be operativelyconnected to actuation structure that extends proximally to the proximalregion 14, to permit an operator to rotate the inner hypotube 42.

Conversely, as shown in FIG. 6, the outer hypotube 44 may be contractedin diameter relative to the inner hypotube 42 such that a new annulargap 52 appears between the outer hypotube 44 and the polymeric layer 46.This can be accomplished, for example, by rotating the outer hypotube 44to decrease the diameter of the outer hypotube 44. In some instances,the outer hypotube 44 may extend proximally to the proximal region 14(see FIG. 1), or may be operatively connected to actuation structurethat extends proximally to the proximal region 14, to permit an operatorto rotate the outer hypotube 44.

FIGS. 7 through 12 illustrate embodiments of the invention in whichinflatable elements are deployed within catheters to provide foradjustable stiffness. In FIG. 7, a catheter 54 includes an elongateshaft 56. As discussed previously with respect to FIG. 1, the elongateshaft 56 may be a polymeric shaft and may include a single polymericlayer, two polymeric layers, or several polymeric layers, reinforcinglayers, and the like. A lumen 58 extends through the interior of theelongate shaft 56, which can be formed of any suitable polymer orpolymers.

An elongate inflation tube 60 is deployed within the lumen 58. In someinstances, the elongate inflation tube 60 may be integrally formedwithin the elongate shaft 56. In some cases, the elongate inflation tube60 may be separately formed and subsequently secured within the lumen 58using any suitable attachment technique. As seen in FIG. 7, the elongateinflation tube 60 is deflated. The elongate inflation tube 60 can beformed of any suitable polymer or polymers.

Turning to FIG. 8, the elongate inflation tube 60 has been inflated. Theelongate inflation tube 60 can be seen as extending at leastsubstantially the entire length of the elongate shaft 56, from aproximal region 62 to a distal region 64. In some instances, theelongate inflation tube 60 can be considered as extending proximallysufficiently far to be in fluid communication with the hub 22 (see FIG.1), so that inflation fluid may be introduced into the elongateinflation tube 60. Any suitable fluid may be used, although saline is anexemplary fluid. Saline is biocompatible, which is important if arupture occurs. Moreover, as an aqueous solution, saline is largelyincompressible.

In the illustrated embodiment, the elongate inflation tube 60 has aradial cross-section that is at least substantially circular in shape,and that remains at least substantially constant across the length ofthe elongate inflation tube 60. In some instances, it is contemplatedthat the elongate inflation tube 60 may have a non-circular radialcross-section. For example, the elongate inflation tube 60 may have anovoid or even polygonal radial cross-section.

In some instances, it is contemplated that the elongate inflation tube60 may have a radial cross-section that changes size across the lengththereof. For example, the elongate inflation tube 60 may have a smallerradial cross-section within the distal region 64 and a larger radialcross-section within the proximal region 62. In some instances, theelongate inflation tube 60 may have two, three or more distinct regions,each region having a distinctive radial cross-section size and/or shape.

It can be seen that the elongate inflation tube 60 can have relativelylittle impact on the flexibility of the elongate shaft 56 when deflated.When the elongate inflation tube 60 is inflated or pressurized, however,the elongate shaft 56 will become relatively less flexible, orrelatively more stiff.

FIG. 9 shows a catheter 66 that includes an elongate shaft 68. Theelongate shaft 68 may be a polymeric shaft and may include a singlepolymeric layer, two polymeric layers, or several polymeric layers,reinforcing layers, and the like. A lumen 70 extends through theinterior of the elongate shaft 68, which can be formed of any suitablepolymer or polymers.

A first elongate inflation tube 70 and a second elongate inflation tube72 are deployed within the lumen 70. In some instances, the firstelongate inflation tube 70 and the second elongate inflation tube 72 maybe integrally formed within the elongate shaft 68. In some cases, thefirst elongate inflation tube 70 and the second elongate inflation tube72 may be separately formed and subsequently secured within the lumen 68using any suitable attachment technique. Each of the first elongateinflation tube 70 and the second elongate inflation tube 72 may beformed of any suitable material.

As illustrated, the first elongate inflation tube 70 and the secondelongate inflation tube 72 have been inflated or pressurized, and can beseen as being at least substantially parallel with each other. In somecases, the first elongate inflation tube 70 and the second elongateinflation tube 72 may be arranged at an angle with respect to eachother. Each of the first elongate inflation tube 70 and the secondelongate inflation tube 72 can be seen as extending at leastsubstantially the entire length of the elongate shaft 68, from aproximal region 76 to a distal region 78.

In some instances, the first elongate inflation tube 70 and the secondelongate inflation tube 72 can each be considered as extendingproximally sufficiently far to be in fluid communication with the hub 22(see FIG. 1), so that inflation fluid may be introduced. Any suitablefluid may be used, although saline is an exemplary fluid.

In FIG. 10, a catheter 80 can be seen as including an elongate shaft 82.The elongate shaft 82 may be a polymeric shaft and may include a singlepolymeric layer, two polymeric layers, or several polymeric layers,reinforcing layers, and the like. A lumen 84 extends through theinterior of the elongate shaft 82, which can be formed of any suitablepolymer or polymers.

A first elongate inflation tube 86 and a second elongate inflation tube88 are deployed within the lumen 84. In some instances, the firstelongate inflation tube 86 and the second elongate inflation tube 88 maybe integrally formed within the elongate shaft 82. In some cases, thefirst elongate inflation tube 86 and the second elongate inflation tube88 may be separately formed and subsequently secured within the lumen 68using any suitable attachment technique. The first elongate inflationtube 86 and the second elongate inflation tube 88 can be formed of anysuitable polymer or polymers.

As illustrated, the first elongate inflation tube 86 and the secondelongate inflation tube 88 have been inflated or pressurized. The secondelongate inflation tube 88 can be seen as extending at leastsubstantially the entire length of the elongate shaft 82, from a distalregion 90 to a proximal region 92. The first elongate inflation tube 86,however, terminates at a position 94 that is well short of the distalregion 90. In some instances, it may be desirable to be able totemporarily provide additional stiffness to the proximal region 92 whileretaining a relatively greater level of flexibility within the distalregion 90.

In some instances, the first elongate inflation tube 86 and the secondelongate inflation tube 88 can each be considered as extendingproximally sufficiently far to be in fluid communication with the hub 22(see FIG. 1), so that inflation fluid may be introduced. Any suitablefluid may be used, although saline is an exemplary fluid.

FIG. 11 shows a catheter 96 having an elongate shaft 98. The elongateshaft 98 may be a polymeric shaft and may include a single polymericlayer, two polymeric layers, or several polymeric layers, reinforcinglayers, and the like. A lumen 100 extends through the interior of theelongate shaft 98, which can be formed of any suitable polymer orpolymers.

An elongate annular inflation ring 102 is deployed within the lumen 100.In some instances, the elongate annular inflation ring 102 may beintegrally formed within the elongate shaft 98. In some cases, theelongate annular inflation ring 102 may be separately formed andsubsequently secured within the lumen 100 using any suitable attachmenttechnique. The elongate annular inflation ring 102 can be formed of anysuitable polymer or polymers.

As seen, the elongate annular inflation ring 102 is inflated orpressurized. The elongate annular inflation ring 102 can extend at leastsubstantially the entire length of the elongate shaft 98, from aproximal region 104 to a distal region 106. In some instances, theelongate annular inflation ring 102 can be considered as extendingproximally sufficiently far to be in fluid communication with the hub 22(see FIG. 1), so that inflation fluid may be introduced into theelongate annular inflation ring 102. Any suitable fluid may be used,although saline is an exemplary fluid.

FIG. 12 shows a catheter 108 having an elongate shaft 110. The elongateshaft 110 may be a polymeric shaft and may include a single polymericlayer, two polymeric layers, or several polymeric layers, reinforcinglayers, and the like. A lumen 112 extends through the interior of theelongate shaft 110, which can be formed of any suitable polymer orpolymers.

An elongate inflation ring 114 is deployed within the lumen 112. In someinstances, the elongate inflation ring 114 may be integrally formedwithin the elongate shaft 110. In some cases, the elongate inflationring 114 may be separately formed and subsequently secured within thelumen 112 using any suitable attachment technique. The elongateinflation ring 114 can be formed of any suitable polymer or polymers.

The elongate annular inflation ring 102 (FIG. 11) has at least asubstantially constant dimension. In contrast, the elongate inflationring 114 has a varying dimension. In some instances, the elongateinflation ring 114 can have a relatively thinner dimension along oneside (top, as illustrated) and a relatively thicker dimension alonganother side (bottom, as illustrated). This can be useful if it isdesired to provide relatively greater stiffness along one side of thecatheter 108 and relatively reduced stiffness along another side of thecatheter 108.

As seen, the elongate inflation ring 114 is inflated or pressurized. Theelongate inflation ring 114 can extend at least substantially the entirelength of the elongate shaft 110, from a proximal region 116 to a distalregion 118. In some instances, the elongate inflation ring 114 can beconsidered as extending proximally sufficiently far to be in fluidcommunication with the hub 22 (see FIG. 1), so that inflation fluid maybe introduced into the elongate inflation ring 114. Any suitable fluidmay be used, although saline is an exemplary fluid.

FIGS. 13 and 14 illustrate an embodiment in which a swellable materialsuch as a hydrogel is used to provide a catheter with adjustablestiffness. In FIG. 13, a portion of a catheter 120 includes an innerpolymer layer 122 and an outer polymer layer 124. The inner polymerlayer 122 and the outer polymer layer 124 can each independently beformed of any suitable polymer or polymers. A gap 126 is disposedbetween the inner polymer layer 122 and the outer polymer layer 124. Alayer or coating 128 of a swellable material is disposed within the gap126. As seen in this Figure, the coating 128 is dry.

In FIG. 14, the coating 128 of swellable material has been caused toswell, thereby eliminating the gap 126 seen in FIG. 13. The coating 128can be caused to swell by contacting the coating 128 with an appropriateliquid. If, for example, the coating 128 is a hydrogel, it can be causedto swell simply by contacting the coating 128 with water. In someinstances, the gap 126 (FIG. 13) can be considered as extendingproximally sufficiently far to be in fluid communication with the hub 22(see FIG. 1), so that an appropriate liquid such as water may beintroduced.

Examples of suitable swellable materials include hydrophilic polymers. Ahydrophilic polymer is a polymer that attracts or binds water moleculeswhen the polymer is placed in contact with an aqueous system. Examplesof aqueous systems that can provide water molecules that can bind to ahydrophilic polymer include blood and other bodily fluids. When ahydrophilic polymer comes into contact with such a system, watermolecules can bind to the polymer via mechanisms such as hydrogenbonding between the water molecules and substituents or functionalgroups present within or on the polymer.

One class of polymers that can be considered as hydrophilic includesionomer polymers. An ionomer polymer is a polymer that can be consideredas containing covalent bonds between elements within a chain whilecontaining ionic bonds between chains. An ionomer polymer is a polymerthat has charged functional groups appended to the polymer chain. Thecharged functional groups can be positively charged, in which case thepolymer can be referred to be a cationomer, or the functional groups canbe negatively charged, in which case the polymer can be referred to asan anionomer.

An ionomeric polymer can be formed using a variety of negatively chargedfunctional groups. The negatively charged functional group can be addedto a previously formed polymer, or the negatively charged functionalgroups can be part of one or more of the monomers used to form theionomeric polymer.

Examples of suitable negatively charged functional groups includesulfonates and carboxylates. The ionomeric polymer can, in particular,include sulfonate functional groups. These groups are negatively chargedand can readily hydrogen bond sufficient amounts of water when broughtinto contact with a source of water such as an aqueous system.

Further examples of suitable materials include nonionic polyetherpolyurethanes available commercially under the HYDROSLIP® name. Anothersuitable material includes nonionic aliphatic polyether polyurethanesavailable commercially under the TECOGEL® name. Examples of othersuitable nonionic polymers include polymers such as poly (hydroxymethacrylate), poly (vinyl alcohol), poly (ethylene oxide), poly(n-vinyl-2-pyrolidone), poly (acrylamide) and other similar materials.

FIGS. 15 through 17 illustrate embodiments of the invention in whichcatheters can enjoy adjustable stiffness through the use of externalsheaths that may be slidably disposed over the catheters.

FIG. 15 shows a catheter 130 including an elongate shaft 132 and astiffness sheath 134 slidably disposed over the elongate shaft 132. Theelongate shaft 132 may be a polymeric shaft and may include a singlepolymeric layer, two polymeric layers, or several polymeric layers,reinforcing layers, and the like. Any suitable polymer or polymers canbe used. The stiffness sheath 134 may be formed of any suitably stiffpolymeric or metallic material.

In FIG. 16, a catheter 136 includes the elongate shaft 132 as discussedwith respect to FIG. 15. A first stiffness sheath 138 is slidablydisposed over the elongate shaft 132, while a second stiffness sheath140 is slidably disposed over the first stiffness sheath 138. In someinstances, each of the first stiffness sheath 138 and the secondstiffness sheath 140 may independently be moved either distally orproximally over the elongate shaft 132 to provide a desired degree ofstiffness. Each of the first stiffness sheath 138 and the secondstiffness sheath 140 may be formed of any suitably stiff polymeric ormetallic material.

In FIG. 17, a catheter 142 includes the elongate shaft 132 as discussedwith respect to FIG. 15. A tapered or frustoconical-shaped stiffnesssheath 144 is slidably disposed over the elongate shaft 132. Thestiffness sheath 144 has a narrow end 146 and a wide end 148 and canprovide, as a result, a gradual change in stiffness. The stiffnesssheath 144 can be formed of any suitably stiff polymeric or metallicmaterial.

FIG. 18 illustrates an embodiment of the invention employing a number ofstiffness filaments. A catheter 150 includes an elongate shaft 152. Theelongate shaft 152 may be a polymeric shaft and may include a singlepolymeric layer, two polymeric layers, or several polymeric layers,reinforcing layers, and the like. A lumen 154 extends through theelongate shaft 152, which can be formed of any suitable polymer orpolymers.

The catheter 150 includes a number of elongate apertures 156 disposedwithin the elongate shaft 152. It can be seen that the elongateapertures 156 extend longituidinally within the elongate shaft 152. Theelongate apertures 156 can be evenly spaced out about the circumferenceof the elongate shaft 152. Any number of elongate apertures 156 may beprovided. At least some of the elongate apertures 156 include astiffness-enhancing filaments 158 slidably deployed within the elongateapertures 156.

Depending on the performance requirements, one or more of thestiffness-enhancing filaments 158 may be inserted into, removed from, orslide within an appropriate and corresponding elongate aperture 156. Insome instances, the stiffness-enhancing filaments 158 may be wiresformed of any suitable material such as Nitinol, stainless steel,titanium, aluminum, cobalt chromium or any other suitable metal.

FIGS. 19 and 20 illustrate use of an electro-active polymer in providingvariable stiffness to a catheter. FIG. 19 shows a catheter 174 having anelongate shaft 176 that includes one or more polymeric layers. A seriesof flaps 178 have been cut into the elongate shaft 176, and extend intoa lumen 180. At least the flaps 178 include an electro-active polymer.It should be noted that the size of the flaps 178 relative to theelongate shaft 176 has been exaggerated for illustrative purposes. Inthis configuration, which can be considered to be a relaxedconfiguration, the flaps 178 provide a level of flexibility to theelongate shaft 176.

In FIG. 20, a current has been applied. Consequently, the flaps 178 havebeen actuated from the position seen in FIG. 19, in which the flaps 178extend into lumen 180, to a position in which the flaps 178 align withthe elongate shaft 176 and thereby improve the column strength of theelongate shaft 176.

It should be noted that in some instances, it is contemplated that atleast a portion of elongate shaft 12 (see FIG. 1) may be formed from orinclude a layer of an electrostatically actuatable material such as anelectro-active polymer, a polymer including buckytubes, or perhaps aliquid crystal polymer. It is contemplated that such materials may, ifsubjected to an electrical current, change the relative stiffness of acatheter containing such a material.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of theinvention. The invention's scope is, of course, defined in the languagein which the appended claims are expressed.

1. An adjustable catheter, the catheter having a distal region and aproximal region, the catheter comprising: an elongate polymeric shaftextending from the proximal region to the distal region; a firstspiral-cut hypotube disposed within the elongate polymeric shaft; and asecond spiral-cut hypotube disposed about the first spiral-cut hypotube;wherein the first spiral-cut hypotube translates from a relativelyproximal position to a relatively distal position, thereby increasingstiffness of the distal region of the catheter; wherein the secondspiral-cut hypotube has a relaxed position in which the secondspiral-cut hypotube has a relaxed inner diameter, the first spiral-cuthypotube has a relaxed position in which the first spiral-cut hypotubehas a relaxed outer diameter, and the relaxed inner diameter of thesecond spiral-cut hypotube is larger than the relaxed outer diameter ofthe first spiral-cut hypotube; and wherein the second spiral-cuthypotube is adapted such that rotating the second spiral-cut hypotubewith respect to the first spiral-cut hypotube causes the second hypotubeto constrict onto the first spiral-cut hypotube.
 2. An adjustablecatheter, the catheter having a distal region and a proximal region, thecatheter comprising: an elongate polymeric shaft extending from theproximal region to the distal region; a first spiral-cut hypotubedisposed within the elongate polymeric shaft and a second spiral-cuthypotube disposed about the first spiral-cut hypotube; wherein the firstspiral-cut hypotube translates from a relatively proximal position to arelatively distal position, thereby increasing stiffness of the distalregion of the catheter; wherein the second spiral-cut hypotube has arelaxed position in which the second spiral-cut hypotube has a relaxedinner diameter, the first spiral-cut hypotube has a relaxed position inwhich the first spiral-cut hypotube has a relaxed outer diameter, andthe relaxed inner diameter of the second spiral-cut hypotube is largerthan the relaxed outer diameter of the first spiral-cut hypotube; andwherein the first spiral-cut hypotube is adapted such that rotating thefirst spiral-cut hypotube with respect to the second spiral-cut hypotubecauses the first spiral-cut hypotube to expand onto the secondspiral-cut hypotube.
 3. An adjustable catheter, the catheter having adistal region and a proximal region, the catheter comprising: anelongate polymeric shaft extending from the proximal region to thedistal region; a first spiral-cut hypotube disposed within the elongatepolymeric shaft and a second spiral-cut hypotube disposed about thefirst spiral-cut hypotube; wherein the first spiral-cut hypotubetranslates from a relatively proximal position to a relatively distalposition, thereby increasing stiffness of the distal region of thecatheter; and wherein the first spiral-cut hypotube and the secondspiral-cut hypotube are adapted such that each are independentlytranslatable relative to each other.
 4. An adjustable catheter, thecatheter having a distal region and a proximal region, the cathetercomprising: an elongate polymeric shaft extending from the proximalregion to the distal region; a first spiral-cut hypotube disposed withinthe elongate polymeric shaft and a second spiral-cut hypotube disposedabout the first spiral-cut hypotube; wherein an outer surface of thefirst spiral-cut hypotube is spaced apart from an inner surface of thesecond spiral-cut hypotube; wherein relative movement between the firstspiral-cut hypotube and the second spiral-cut hypotube causes the distalregion to become more stiff; wherein relative movement between the firstspiral-cut hypotube and the second spiral-cut hypotube createsinterference between the first spiral-cut hypotube and the secondspiral-cut hypotube; and wherein relative movement between the firstspiral-cut hypotube and the second spiral-cut hypotube consists ofcontracting the second spiral-cut hypotube onto the outer surface of thefirst spiral-cut hypotube.
 5. The adjustable catheter of claim 4,wherein the second spiral-cut hypotube is contracted onto the outersurface of the first spiral-cut hypotube by rotating the secondspiral-cut hypotube.
 6. An adjustable catheter, the catheter having adistal region and a proximal region, the catheter comprising: anelongate polymeric shaft extending from the proximal region to thedistal region; a first spiral-cut hypotube disposed within the elongatepolymeric shaft and a second spiral-cut hypotube disposed about thefirst spiral-cut hypotube; wherein an outer surface of the firstspiral-cut hypotube is spaced apart from an inner surface of the secondspiral-cut hypotube; wherein relative movement between the firstspiral-cut hypotube and the second spiral-cut hypotube causes the distalregion to become more stiff; wherein relative movement between the firstspiral-cut hypotube and the second spiral-cut hypotube createsinterference between the first spiral-cut hypotube and the secondspiral-cut hypotube; and wherein relative movement between the firstspiral-cut hypotube and the second spiral-cut hypotube consists ofexpanding the first spiral-cut hypotube into contact with the innersurface of the second spiral-cut hypotube.
 7. The adjustable catheter ofclaim 6, wherein the first spiral-cut hypotube is expanded into contactwith the inner surface of the second spiral-cut hypotube by rotating thefirst spiral-cut hypotube.
 8. The adjustable catheter of claim 6,wherein the first spiral-cut hypotube is expanded into contact with theinner surface of the second spiral-cut hypotube by axially compressingthe first spiral-cut hypotube.